Can someone please explain to me in simple terms Einsteins theory of relativity, also known as time dialation?

Time dilation. Time dilation, in the theory of special relativity, the “slowing down” of a clock as determined by an observer who is in relative motion with respect to that clock.The world's most accurate clock has neatly shown how right Albert Einstein was 100 years ago, when he proposed that time is a relative concept and the higher you live above sea level the faster you should age. Einstein's theory of relativity states that time and space are not as constant as everyday life would suggest.The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature.

Explanation:

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.